Sram 11 Spd - why still use the 1/2" chain standard?

I was thinking, the XX1 (and the upcoming X01) both have a 10t smallest cog int he back. That's because a 9t sprocket (it was tested by Sram/specialized using the Shimano commuter grouppo cog) had a polygon effect, that was too noticeable for enjoyable cycling. I still fear a 42-10 range is a bit small for the alps (a 22-36 combo in front covers it better, though you can just live with a 22-32, both on a 32-11 cassette, though a 36-11 goves you even more advantages then).

There was talk of the possibility that the XX1 der. can go up to 44t, which would be even better.

Now, if we go from a 1/2" chain to a 10 mm pitch chain, we can get an 11t sprocket int he rear, that has the same diameter as a 1/2" 9t sprocket. That would also lower the diameter of the biggest sprocket (to an equivalent of a 38t size in 1/2" pitch). The system would then be lighter and more compact.

Yes, there is the problem of durability, but if Shimano got it to work 30+ years ago (albeit on the road, but still, 30 years), i guess we could make it work today for a MTB. The negatives of custom sprockets, chains and everything else (that i could read in some old topics) completely fall appart, since we have custom sprockets and chains (with derailleurs even) for 11 speed systems even on the standard 1/2" pitch.

More or less i'm only wondering, wass a smaller chain even considered by Sram and if yes, how quickly was it thrown out the window?

Well, the problem with what you're suggesting is that the 'pulleys' (sprockets) in your system would still be the same diameter, just with more chain wrap. It would help with wear ( theoretically) but perform no other function. That would be because the torque delivered is effected by their relative size, not tooth count.

Not 100% sure we're talking about the same thing here, but that's what I took away from your post.

No, it was said that a 9t sprocket caused the polygon effect to be too noticeable. Going to a 11t sprocket with the same diameter (the same diameter is the whole point of it) still gives you a high high gear without the polygon effect.